1. Field of the Invention
The present invention relates to a touch sensing device, a touch sensing unit, a storage medium and a touch sensing method.
2. Related Art
Heretofore, velocity information representing the strength or weakness of a sound to be played by an electronic musical instrument has been sensed, for example, as follows in an electronic piano. A first contact and a second contact are provided below each key of the electronic piano. The first contact and the second contact are closed subject to mutually different key press amounts. The electronic piano measures a time difference between the closing timings of the first contact and the second contact, and detects velocity information on the basis of the time difference.
Then the electronic piano immediately emits a sound from a sound source in accordance with the velocity information.
Thus, a sound emission start time in the electronic piano is just after the velocity information is detected, that is, substantially at the timing of closing of the second contact. The second contact is disposed some way to the upper side of a lower limit of the key. That is, a conventional electronic piano starts sound emission before a key is pressed to its lower limit.
FIG. 18 is a graph describing timings from when a key is pressed until a sound is emitted in a conventional electronic piano.
As shown in FIG. 18, because the conventional electronic piano starts sound emission processing when the second contact is closed, sound is emitted before the key is fully pressed to the lower limit.
Fundamentally, it is ideal if the sound emission timings of an electronic piano match the sound emission timings of an acoustic piano. When a key is pressed in an acoustic piano, this movement is transmitted to the action, the hammer moves, the head strikes the string, and vibrations of the string emit sound, via the bridge and soundboard of the piano. The relationship between key press amounts and sound emission in an acoustic piano can be adjusted but, as described above, is structurally complex. Consequently, because a conventional electronic piano that emits sound at the closing timing of a second contact and an acoustic piano have different structures, the respective sound emission timings are different.
Moreover, differences between the sound emission timings of an electronic piano and an acoustic piano vary depending on the pitches of the sounds that are emitted and the strengths of key presses.
In a conventional electronic piano, with regard to preventing an increase in weight of the piano, maintaining rapid playability with key return times, avoiding malfunctions that are caused by complex action structures, and the like, the weights of the keys in the stationary condition are lighter and the inertial moments of the keys when pressed are lower than in an acoustic piano. The weight of a key in the stationary condition provides a reaction force when a key press from the stationary condition is begun, and provides an influence on an extremely weak key press operation. The inertial moment of a key provides a reaction force during a key press operation, and provides an influence on a strong key press operation.
FIG. 19 is a graph describing the difference between sound emission timings in a conventional electronic piano and sound emission timings in an acoustic piano.
FIG. 19 shows the two sound emission timings when a key is pressed with the same strength on an electronic piano and on an acoustic piano.
As described above, the key of the electronic piano has a lighter weight than the key of the acoustic piano and the inertial moment of the key during the key press is lower. Therefore, even if pressed with the same strength as the key of the acoustic piano, the key of the electronic piano is pressed down more quickly. Consequently, the sound emission timing of the electronic piano is earlier than the desired sound emission timing of the acoustic piano.
Accordingly, Japanese Unexamined Patent Application, Publication No. H08-234733 discloses an electronic instrument in which sound emission instruction information is detected by time difference sound emission processing that is executed by a central processing unit (CPU), after which a duration until a note is actually generated is delayed by a duration based on pitch information, timbre information or the like of the sound to be emitted.
Japanese Unexamined Patent Application, Publication No. H07-92971 proposes an electronic piano that, using a table that relates velocities with delay durations, specifies a delay duration by sound emission timing correction processing executed by a CPU, and emits a sound after the delay duration has passed.
According to the electronic instrument of Japanese Unexamined Patent Application, Publication No. H08-234733 and the electronic piano of Japanese Unexamined Patent Application, Publication No. H07-92971, a duration from a key being pressed until a sound is emitted may be adjusted by a CPU executing processing in software.
However, recent electronic instruments generate many sounds at the same time, and the processing burden on embedded CPUs is increasing. As a consequence, accurately managing delay durations of sound emission timings simply by employing processing based on a CPU executing software as in Japanese Unexamined Patent Application, Publication No. H08-234733 and Japanese Unexamined Patent Application, Publication No, H07-92971 has become difficult.
FIG. 20 is a graph describing timings from when a key is pressed until a sound is emitted in a conventional electronic piano in which a sound emission timing is delayed by processing in software.
The conventional electronic piano that delays the sound emission timing by processing in software counts a correction duration for delaying the sound emission timing from when the second contact is closed, and emits the sound after the correction duration has passed.
However, the processing burden on the CPU of this electronic piano varies depending on the number of sounds to be emitted at the same time. Consequently, as shown in FIG. 20, there is inconsistency in the counting of correction durations depending on the variations in the processing burden on the CPU. As a result, there is inconsistency in sound emission timings. Because this inconsistency changes in accordance with variations in the processing burden on the CPU, a player may not be able to adapt to the inconsistency, which is a hindrance to playing.